Running 10.7.5 on a mac mini and it's constantly hanging up

I am having trouble with my browsers, mail, printer and quick books all running slow, hanging up, quitting and just plain being a pain. I don't run any major applications on this machine, just office type stuff. I have to force quit all the time. There is a ton of free space on the hard drive.

Any suggestions for some housekeeping I could do on my own before taking it to the medic? I am going to verify and repair permissions. Beyond that I always feel better with a little hand holding.

Thanks!

Mac Mini - mid 2011

2 GB 1333 MHz DDr3

serial CO7G5MDYDJD0

Lion 10.7.5 (11G63)